Commercially-available coffee concentrates are typically manufactured by partially dehydrating aqueous extracts of solid flavor sources. Alternatively, such products are manufactured by dissolving the dried extracts in water. These products are commonly subjected to thermal processing and/or fortification with chemical preservatives to improve microbiological stability and increase shelf life.
Liquid aqueous coffee concentrates have been commercially available for decades, but these products still suffer from widely-known shortcomings related to their composition and handling requirements. For example, initial flavor quality may be greatly inferior to freshly-brewed coffee and shelf life at room temperature may be very short, requiring refrigerated or frozen distribution and storage. It is also known that these types of products are often chemically unstable, as generally evidenced by increasing acidity and sedimentation, and decreasing flavor quality, during storage. Aqueous liquid tea concentrates are also known, and these products are similarly prone to flavor degradation and sedimentation during storage.
Attempts have been made to improve the chemical stability of aqueous coffee concentrates, but the methods generally require use of expensive or complicated processing, chemical treatments, or chemical preservatives. Freezing may reduce or prevent some instability problems but at a cost of increased energy consumption and inconvenience because frozen products must be thawed before use. Under some conditions, freezing may also increase reactions or sedimentation because solutions undergo freeze-concentration into a progressively smaller volume of liquid, thereby increasing the potential for solute interactions. Freezing and frozen storage typically require the use of temperatures well below the freezing point of pure water to effectively solidify such freeze-concentrated solutions, further increasing costs and time required for processing and thawing.